1. Field of the Invention
The present invention relates to an ultrasonic transducer which generates an ultrasonic vibration in a bonding apparatus used in a semiconductor manufacturing apparatus.
2. Prior Art
Wire bonding apparatuses, bump bonding apparatuses and single-point bonding apparatuses are known to be used in semiconductor manufacturing apparatuses. In such apparatuses, an ultrasonic transducer is utilized in order to apply an ultrasonic vibration to the bonding parts. In this regard, an ultrasonic press-bonding system which joins the bonding parts by combining ultrasonic vibration and a load, and a combination ultrasonic and thermal press-bonding system which applies an ultrasonic vibration while heating the bonding parts to, for instance, approximately 200xc2x0 C., etc., are known.
Langevin type transducers (bolt-fastened transducers) are known as conventional ultrasonic transducers for use in bonding apparatuses. Such transducers are generally constructed from a bolt-fastened vibrator (Langevin vibrator), a horn through which the ultrasonic wave generated by this vibrator is transmitted, and a bonding tool which is attached to the tip end of this horn.
Bolt-fastened vibrators are ordinarily constructed from a plurality of electrostriction elements, a plurality of electrodes that are installed between these electrostriction elements, a bolt which is passed through the electrostriction elements and electrodes, and a pair of blocks which firmly hold a laminated body comprising the electrostriction elements, etc., via the bolt. In this structure, the side surfaces of the respective electrostriction elements are exposed to the outside, and the respective electrodes are connected to signal wires on the side surface of the laminated body.
Since the signal wire connections are done on the side surface of the transducer, these connecting portions form a part of the space occupied by the transducer. As a result, the transducer, particularly its rear end portion, cannot be formed with a small diameter.
In semiconductor manufacturing apparatuses, other mechanisms (e.g., a sample holding mechanism, etc.) are present beneath the transducer when the bonding tool is caused to contact the bonding parts; accordingly, physical interference (collision) between these mechanisms and the ultrasonic transducer must be avoided. Consequently, it is desirable to reduce the diameter of the ultrasonic transducer. In other words, it is desirable to reduce the size of the transducer in order to insure or enlarge the space through which movement is possible.
Furthermore, it is also desirable to lighten the weight of the ultrasonic transducer in order to reduce the driving load and improve the driving response characteristics during the movement of the ultrasonic transducer. In conventional ultrasonic transducers, since the laminated body comprising the electrostriction elements, etc. is exposed to the outside, this laminated body is directly exposed to heat radiation from the heater that is provided beneath the ultrasonic transducer. As a result, there is a danger of a change in the vibration characteristics caused by heating.
Furthermore, in conventional ultrasonic transducers, a connecting part is located between the block on the front side of the vibrator and the horn. If a large cross-sectional step is present here, the vibration transmission efficiency drops.
Japanese Patent Application Laid-Open (Kokai) No. H10-303240 discloses an ultrasonic transducer in which a hollow section is formed inside the horn in the axial direction of the horn. This hollow section is for reducing the weight of the ultrasonic transducer; and a Langevin vibrator is installed on the rear end of the horn. Thus, in this prior art, the surfaces of the electrostriction elements are exposed to the outside, and the electrostriction elements are connected to the signal wires on the outer surfaces of the electrostriction elements. Accordingly, it is difficult to reduce the diameter of the ultrasonic transducer (especially the rear end portion), and it has problems similar to those described above.
Accordingly, the present invention was created in light of the above-described conventional problems; and one object of the present invention is to reduce the size of the ultrasonic transducer, especially the rear end portion.
Another object of the present invention is to avoid wire connections on the outer surface of the laminated body in the ultrasonic transducer.
Still another object of the present invention is to make it possible to embed the laminated body inside the horn in the ultrasonic transducer and also to achieve a reduction in the weight of the ultrasonic transducer.
In order to accomplish the above objects, in the present invention which is for an ultrasonic transducer that is installed in a bonding apparatus, the transducer includes a horn body and a vibrator assembly; and the horn body has a bonding tool attached to the tip end portion and a first hollow section formed in at least the rear end portion, and the vibrator assembly is accommodated in the first hollow section and generates an ultrasonic vibration.
In above structure, the first hollow section is formed in the rear end portion of the horn body, and the ultrasonic wave generated by the vibrator assembly inside this hollow section is transmitted to the bonding tool via the horn body. Then, the ultrasonic vibration of the bonding tool is transmitted to the bonding parts.
In the present invention, since the vibrator assembly is accommodated inside the rear end portion of the horn body, the shape of the rear end portion of the horn body can be simplified, and the diameter of this rear end portion can be reduced. Furthermore, the present invention is also advantageous in that the vibrator assembly can be physically and thermally protected. In addition, the working characteristics are good, and the manufacturing cost can be reduced.
Preferably, the ultrasonic transducer of the present invention includes a fastening member which is inserted via a rear end opening formed in the rear end portion of the horn body so as to push the vibrator assembly into the first hollow section and fastens the vibrator assembly in place. The internal circumferential wall of the first hollow section in the horn body functions as a tightening member between both ends of the vibrator assembly.
The circumferential wall has, for example, a cylindrical shape. If necessary, one or more openings may be formed in this circumferential wall. It is desirable that the horn body including the circumferential wall be formed as an integral unit. In such a structure, the number of components can be reduced so that manufacturing costs is reduced, and the ultrasonic vibration transmission efficiency is increased. It is desirable that the fastening member be inserted and installed inside the first hollow section. However, a cap shape, for example, which envelops the rear end portion may also be used.
Preferably, through-holes are respectively formed in the vibrator assembly and fastening member, and a signal line (which is of a conductive material) is connected to the vibrator assembly via the through-holes. Since the signal line is led out from the interior of the horn body, the problems arising from the connection of the signal wires on the outside surface as in conventional devices can be eliminated. More specifically, the size of the rear end portion of the transducer can be reduced, and the space occupied by this rear end portion can be reduced.
Preferably, furthermore, a second hollow section which communicates with the tip end portion from the first hollow section is formed in the horn body. As a result of this second hollow section, the weight of the horn body can be reduced even further, and the conveying load of the transducer can be reduced.
A third hollow section which communicates with both the second hollow section and the outside may be formed in the tip end portion of the horn body. With this structure, the heat dissipating action is further enhanced, and thermal stability can be insured. It is also possible to install a cooling mechanism which forcibly feeds air, etc. into such a hollow section.
Preferably, a flange for holding the ultrasonic transducer is formed on the external surface of the horn body so as to positionally correspond to the first hollow section. In this case, it is desirable that the flange be formed in the position of a vibrational node. Here, it is desirable that the flange be formed integral to the horn body.
The above-described ultrasonic transducer to be installed in a bonding apparatus is manufactured by a unique method of the present invention that comprises:
a step in which a first hollow section that communicates with the rear end opening of the horn body is formed in the rear end portion of a horn body,
a process in which a vibrator assembly is inserted into the first hollow section,
a process in which a fastening member is provided in the first hollow section, and the vibrator assembly is fastened in place by being pushed in, and
a process in which a signal wire is connected to a signal line that is led out to the outside from the vibrator assembly through the interior of the horn body.